This is a bit difficult to explain:
First, virtually all single-phase motors in Class I, Division 2
must be
explosionproof no matter what overload protection technique is used. This is because they generally use some form of switching technique to create the initial rotation direction. Three-phase induction motors don't usually have this issue.
Second, a "new" AHJ (FedOSHA) has entered the arena recently. Under the
FedOSHA 29CFR1910.399 definitions of
Acceptable, Accepted, and
Approved:
That is, if a product
can be NRTL certified for a specific pur, it
must be. Until recently general purpose motors were
not NRTL certified; however, in the last few years, some manufacturers have begun to have their motors Class I, Division 2 certified.
NEC [2017] Section 501.125(B)(3) notwithstanding, it is a bit "iffy" not using a NRTL certified motor in Class I, Division 2 and the overload protection technique is irrelevant.